Welded tubular attachment to a pressure member and method of making same



Feb. 4, 1964 o. R. CARPENTER 3,120,400

WELDED TUBULAR ATTACHMENT TO A PRESSURE OF MAKING SAME 2 sheets-sheet 1MEMBER AND METHOD Original Filed Jan. 25, 1954 FIG.5

INVENTOR Oil's/Q. Car Denier ATTORNEY 4, 1964 o. R. CARPENTER 3, 2 ,400

WELDED TUBULAR ATTACHMENT TO A PRESSURE MEMBER AND METHOD OF MAKING SAMEOriginal Filed Jan. 25, 1954 2 Sheets-Sheet 2 FIG.7'

INVENTOR F IG. 8 05 JP Carpenier ATTO R N EY United States Patent 14Claims. (Cl. 285-137) This invention relates to an attachment between atube and a pressure member, more particularly it relates to a novelwelded attachment or joint and method of making same and constitutes acontinuation of the application Serial No. 405,959, filed January 25,1954, and now abandoned.

Many of the present day processes for producing power and chemicalsutilize high temperatures and pressures to accomplish their purposes.The tubular heat exchange equipment which performs in these processes issubject to operating conditions never before encountered, and theattachment of the tubes to pressure members requires very carefulconsiderations as they are most likely to be the initial point offailure. It is therefore important that the attachment be mademechanically sound in such a manner as to withstand high temperatures,pressures, and cyclic variations thereof. Welding of tubes to pressuremembers provides the most sound mechanical attachment. It is to theimprovement of sound welding attachments that this invention applies.

One of the important features of a satisfactory tube attachment is leaktightness under all conditions of operation. It is not to be assumedthat satisfactory mechanical strength will provide a leak tightboundary. Weld deposits, because they are molten when initiallydeposited, upon cooling are considered to be more porous than wroughtmetals, i.e. those that have been drawn, forged, extruded, or Worked insome Way. The porosity is not of such magnitude as to allow aperceptible stream of leaking fluid to be discharged therethrough, butin some types of application even small porosity leakage becomesobjectionable through Weld deposits less than 1 /2 tube Wall thickness(t). A satisfactory well will, therefore, require a leak path throughthe weld deposit of greater than l /zt. Ordinarily the workpieces arewrought metals and as such, these show less propensity for leakage thanthe weld. On this basis the 12 of tube wall is considered roughly equalto 1 /21 of weld deposit.

In summation, a satisfactory tubular attachment to a pressure membershould be both mechanically satisfactory and provide for a minimumleakage.

The present invention is a tube attachment to a pressure member and amethod of making the same, including high quality welding.

Additionally, the invention provides an attachment which is leak proof.

A further advantage of the invention is that the accessibility of theweld root is increased to provide optimum welding conditions.

A still further advantage is that the invention provides a method ofwelding a plurality of tubular elements which involves a long continuousweld path, thereby avoiding the slag inclusions due to frequent stopsand starts which are inherent in welding practices having many shortweld paths.

In addition, the present invention is adaptable for use with any sizetube and/ or tube spacing to improve the efiiciency of the tubularattachment to a pressure member.

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For an understanding of the invention principles, reference is made tothe following detailed description of typical embodiments of theinvention methods as illustrated in the accompanying drawings:

In the drawings:

FIGS. 1, 2 and 3 are sectional elevations of one example of tubularelements and pressure member illustrating suc cessive steps in carryingout the invention method.

FIG. 4 is a plan view illustrating the method of depositing multiplewelds in a single continuous operation.

FIG. 5 is a sectional elevation of the completed tubular attachment ofFIGURES l, 2 and 3.

FIGS. 6, 7 and 8 are sectional elevations of a second illustrativeembodiment of the invention, showing successive steps.

FIGS. 1 through 5 illustrate the progressive steps in making oneembodiment of a tube attachment. A pressure member I is machined orotherwise formed With a number of tube seats into which are fitted thetubes 2. The diameter of each tube seat is slightly larger than thediameter of its tube 2 so that when the tube is placed therethrough thesurface of the tube will be in sliding contact with the surface oft hetube seat. The pressure member 1 is also machined or otherwise formed onits face 3 in such a manner that adjacent and contiguous to each tubeseat there remains a rim of metal which in section appears as a segmentof an arc. This rim of metal is a fillet 5. The tubes 2 are fitted intothe tube seats in such a way that the tube ends 4 extend beyond the face3 of the pressure member 1. The resulting junction of each tube end 4with the face 3 and the fillet 5 of the pressure member 1 in sectionform a right angle with the apex portion being a segment of an arc andhaving the base in a plane substantially perpendicular to thelongitudinal centerline of the tubes 2. After the tubes 2 are positionedin the above described manner each tube is expanded so as to force theouter surface of the tube against the inner surface of the tube seat.Thereby the tubes become mechanically bound to the pressure member. Theexpanding is accomplished by any suitable tool, such as a rotaryexpander or ball drift expander.

In FIG. 2 there is shown the tubes 2 and the pressure member 1 after theprojecting tube ends 4 have been deformed or otherwise formed intofrustums of cones 7. The deforming operation has now so changed thejunction of the tube ends and the tube face so that in section there areformed obtuse angles each having a segment of are 5 at its apex.Therefore, there is now presented, for each tube an annular weld grooveformed by a pressure member face 3, fillet 5, and a conical tube end 7.

FIG. 3 shows the same tube attachments after the next step of theillustrative method. Into the opposite ends of the tubes 2 there hasbeen inserted small tubes 12 which are attached to a manifold 10. Acooling fluid such as air flows from the manifold ltl through tubes 11and is discharged through the tube ends 4. The tube ends 4 and pressuremember 1 are joined by successive weld deposits 8 and 9. During thewelding operation the cooling fluid which flows through the tube ends 4maintains the metal of the tube ends at a low temperature to preventweld metal burnthrough and overheating of the pressure member and tubewall to such an extent that undesirable metal structure results.

In FIG. 5 there is shown a sectional elevation of the completed tubularattachment. To accomplish this re sult, the tube ends shown in FIG. 3are reamed or drilled to the internal diameter 14 of the tubes 2. Thiscauses the removal of the large portion of the metal of the tube ends 4.Each weld juncture 13 upon completion 3 of the method appears, insection, as an obtuse angle having a segment of an are at its apex.

FIG. 4 is a plan view of the pressure member 1 and tubes 2, illustratingthe initial weld deposition pass of the preferred welding operation. Aweld deposition pass is herein defined as a continuous weld metaldeposit which would result from any continuous and uninterrupted meltingof the metal of a weld rod. A weld deposition pass would be completedupon any interruption to a continuous weld path. The weld deposit 8 islaid down during a single pass in a sinuous welding operationcontinuously around a plurality of tube ends, whereby at least asubstantial peripheral portion of each of the pertinent tube ends isjoined to the pressure member. Further passes would be made until thereis sufiicient weld metal uniting the tubes 2 to the pressure member 1throughout the entire circumference of the welding groove to give amechanically sound and leak proof tubular attachment. Each weld pass maybe made as shown in FIG. 4 or alternately could be made by encirclingthe complete periphery of the tube or any portion thereof and then goingon to an adjacent tube. The important feature of welding in this manneris that the weld metal is deposited continuously over a path ofsubstantial length. The continuous deposition of weld metal reduces thenumber of stops and starts which would have to be made if each tube werewelded individually. These stops and starts are reduced in order tominimize the number of slag inclusions and other weld imperfectionswhich result from them. In the installation where small tubes, in theorder of one half inch diameter, are joined it is estimated that thenumber of stops and starts can be reduced by as much as 75 percent. Thewelds resulting from this method of deposition will accordingly beimproved by that same percentage.

The method illustrated in FIGS. 1-5 is primarily directed to thesecuring of a high quality weld. This weld is made possible by formingthe weld groove so that there is an obtuse angle presented to thewelder. The obtuse angle gives the welder complete accessibility duringall phases of the welding process. By virtue of this fact the welder canexercise the proper amount of vigilance to assure a weld free ofimperfections. Also, because the root of the weld, i.e., apex of theweld angle, presents a broad weld base due to the fillet 5,imperfections in the first weld deposit are minimized. The combinationof the apex angle and the fillet create conditions which accrue to thebenefit of the welder and makes possible high quality welds.

A second illustrative embodiment of the invention is shown in the FIGS.6-8, involving illustrations of the various steps of the method. In FIG.6 the pressure member has been formed with a tube seat therethrough andin the face there is an annular L shaped groove 13 formed continuouswith the periphery of the tube seat and having the base of the groove ina plane substantially perpendicular to the longitudinal centerline ofthe tube 17. The tube 17 has an end 16 which has been formed with an Lshape annular groove 19 to a depth where there remains a tube wallthickness not greater than 0.125 inch. The tube 17 is positioned in thetube seat of the pressure member 15 so that the base of the L groove 19is in the same plane as the base of the pressure member groove 18. Thetube 17 is next expanded into the pressure member 15. The tube end 16 isthen formed into a frustrum cone 21 (FIG. 7). This action presents aweld groove which in section, has an obtuse angle having a segment of anare as its apex. Weld deposits 23, 24, 25 are then made successively,thereby uniting the tube 17 to the pressure member 15.

In FIG. 8 there is shown the completed attachment in the final formafter reaming or drilling the tube end 16 to the internal diameter 26 ofthe tube 17.

The tube attachment as shown in FIG. 8 is similar to that shown in FIG.5 and is also primarily concerned with the attainment of a good highquality weld. This weld is the direct result of the improved weldaccessibility obtained by the forming of the tube and pressure member insuch a manner that there is an obtuse angle welding groove having asegment of an are at its apex. The welder, during the entire operationcan see the junction of the tube and the pressure member and he cantherefore, exercise a maximum of quality control on the weld. The weldgroove is formed so that there are no sharp corners which may propagateweld cracking under high stress loading.

An important requirement in tube attachments for high pressure and/orhigh temperature heat exchangers, is that the weld attachment be leakproof. The attach ment herein described achieves that result by makingthe length of the junction of the weld metal and the tube greater thanthe thickness of the tube wall. The tube wall being of wrought metal,i.e., that it has been drawn, forged, extruded or worked in some way,has less propensity for fluid leakage than the weld metal and, as can beseen from FIGS. 5 and 8 of the completed joints, the length of the leakpath is substantially greater than the thickness of the tube.

The improved method provides a tube attachment which not only has a highdegree of mechanical strength, but also has excellent leak proofcharacteristics.

It should be understood that the invention as illustrated in the aboveembodiments would not necessarily include all of the described detailsof all of the steps of the illustrative method. For instance, in case ofvery thick tube walls, the frusto-conical tube end might be formed bymachining the tube end and as such would not require machining afterwelding. Also the attachment could be made without the use of fluidcooling during the welding operation.

While in accordance with the provisions of the statutes, I haveillustrated and described herein specific forms of the invention nowknown to me, those skilled in the art will understand that changes maybe made in the form of the apparatus and method disclosed withoutdeparting from the spirit of the invention as covered by my claims andthat certain features of my invention may sometimes be used to advantagewithout a corresponding use of the other features.

What is claimed is:

1. Fusion welded tube attachments to a pressure member which comprises aplurality of tube seats formed through the wall of the pressure member,fillets formed in the face of the pressure member contiguous with theperiphery of the tube seats, frusto-conically shaped tube ends fittedinto said tube seats and so positioned that the conical surfaces aretangent to the arc of the fillets whereby the surfaces of the tube endsprojecting beyond said pressure member and the outer face of saidpressure member form obtuse angled weld grooves with their apexesdefining a segment of an arc, and fusion welds in successive passescompletely uniting said tubes and pressure member, each of said weldpasses being sinuous and continuous around at least a substantialperipheral portion of a plurality of the weld grooves.

2. A method of attaching a tube in the tube seat of a pressure memberwhich includes forming the tube end into a frustum of a cone with thesurfaces of the tube end and a face of the pressure member forming anobtuse angled welding groove, rounding out the surface of the pressuremember at the junction of said tube and pressure member to form a filletcontiguous with the tube end and filling the welding groove with weldmetal to join the tube and pressure member.

3. A method of attaching a plurality of tubes in respective tube seatsof a pressure member which includes forming the tube ends into frustumsof cones with the surfaces of the tubes and a face of the pressuremember forming obtuse angled welding grooves with a tube to weldjunction line greater than 1 121, where t is the wall thickness of thetubes, uniting the tubes and pressure member by successive welddeposition passes, said passes being continuous over a plurality of theweld grooves with the depositions extending over at least substantialperipheral parts of said grooves.

4. A method of attaching a tube to a pressure member which includesforming a tube seat through said member, fitting the tube into the tubeseat to a position where the end of the tube extends beyond the face ofthe pressure member, expanding the tube into the tube seat, forming saidtube end into a frustum of a cone such that the surfaces of the tube endand the face of the pressure member form an obtuse angled welding groovewith a tube to weld junction line greater than 1 /21, where t is thewall thickness of the tube, flowing a cooling fluid through the tube ina direction toward said tube end, uniting the tube and pressure memberby a weld deposit, opening the tube end to the internal diameter of thetubes and maintaining the tube to weld junction line to at least 1 /21.

5. A method of attaching a plurality of tubes to a pressure member whichincludes forming tube seats through said pressure member; formingfillets in the face of said member contiguous with the periphery of thetube seats; fitting tubes into said tube seats to a position where theends of the tubes extend beyond said face of the pressure member;expanding the tubes into the tube seats; forming said tube ends into afrustum of a cone such that the surfaces of the tube ends, the face ofthe pressure member, and the fillets form obtuse angled welding grooveswith their apex being a segment of an arc and with the tube to weldjunction line being greater than l /zt, where t is the wall thickness ofthe tube; flowing a cooling fluid through the tubes in a directiontoward said tube ends; uniting the tubes and pressure member bydepositing welds in said weld grooves; and opening the tube ends to theinternal diameter of the tubes and maintaining the tube to weld junctionline to at least 1 /21.

6. A method of attaching tubes to a pressure member as in claim 5 withthe welds uniting the tubes and pressure member by successive welddeposition passes, said passes being sinuous and continuous over aplurality of the weld grooves with the depositions extending over atleast substantial peripheral parts of said grooves.

7. A method of attaching a tube to a pressure member which includesforming a tube seat through said pressure member, forming an annulargroove in the surface of the member concentric and continguous with thetube seat, forming an annular circumferential groove of L- shaped crosssection in the outer surface of the tube adjacent the end thereof sothat the tube wall thickness is reduced, fitting said tube into the tubeseat to a position such that the base of the L is in the same plane asthe base of the pressure member groove, forming the tube end intofrustum of a cone such that the conical surface and the base of the tubegroove form an obtuse angled welding groove with the apex being asegment of an arc; and filling said welding groove with weld deposit tojoin the tubes and pressure member.

8. A method of attaching a tube to a pressure member which includesforming a tube seat through said pressure member, forming an annulargroove in the surface of the member concentric and contiguous with thetube seat, forming an annular circumferential groove of L-shaped crosssection in the outer surface of the tube adjacent the end thereof sothat the tube wall thickness is reduced, fitting said tube into the tubeseat to a position such that the tube extends beyond the pressure membergroove, expanding the tube into the tube seats, forming the tube endinto frustum of a cone such that the conical surface and the base of thetube groove form an obtuse angled welding groove with the apex being asegment of an arc, flowing a cooling fluid through the tube in adirection toward said tube end, filling said welding groove with welddeposit to join the tube and pressure member, and

'6 opening said tube end to the inner diameter of the tubes;

9. A method of attaching a tube to a pressure member which includesforming a tube seat through said member, forming the tube end and thepressure member face in such a manner that when the tube is fitted intothe tube seat in operative relationship therewith there is formed anobtuse angle weld groove with the tube to Weld junction line beinggreater than l /zt, where t is the wall thickness of the tube, roundingout the surface of said member so that the junction of said tube andmember is defined by a segment of an arc in cross-section continuouswith the tube end, and filling said weld groove with weld metal to jointhe tube and pressure member.

10. A method of attaching a tube to a pressure member which includesforming a tube seat through said member, forming the tube end and thepressure member face in such a manner that when the tube end is fittedinto the tube seat in operative relationship there is formed an obtuseangled welding groove having a tube to weld junction line greater than 1/21, wherein t is the wall thickness of the tube, rounding out thesurface of said member so that the junction of said tube and member isdefined by a segment of an arc and having the base of the angle in aplane substantially perpendicular to the longitudinal center line of thetube, and filling said weld groove with weld metal to join the tube andpressure member.

11. A method of making a fluid tight connection of a plurality of tubesin closely spaced tube seats of a pressure member comprising fitting thetubes into corresponding tube seats with an end of each tube extendingbeyond the end of the adjacent face of the pressure member, expandingeach tube so positioned into its respective tube seat so as to force theouter cylindrical surface of the tube adjacent said extending endthereof against the inner surface of its respective tube seat, andwelding the junction between the extending end of each of said tubes andthe face of the pressure member by a fusion arc weld depositing weldmetal in a continuous sinuous path extending along a substan tialsegmental length of the junctions of successive tubes and the face ofthe member.

12. The method as defined in claim 11, including the step of repeatingsaid fusion arc weld operation along substantially the remainingunwelded segmental lengths of the junctions of said successive tubes andthe face of said member continuous sinuous well path.

13. A method of making a fluid tight connection of a plurality of tubesin closely spaced tube seats of a pressure member comprising, fittingthe tubes into corresponding tube seats with an end of each tubeextending beyond the end of the adjacent face of the pressure member,forming the tube ends into frustums of cones with the surfaces of thetubes and the face of the pressure member to define obtuse angledwelding grooves thereat, and welding the junction between each of saidtubes in the adjacent face of the pressure member by a fusion arc welddepositing weld metal in a continuous, sinuous path extending along asubstantial segmental length of the junctions of successive tubes andthe face of the member.

14. Fusion welded tube attachments to a pressure member which comprisesa plurality of tube seats formed through the wall of the pressuremember, fillets formed in the face of the pressure member contiguouswith the periphery of the tube seats, a tube having an expandedconnection with each of said tube seats, each of said tubes having anend portion extending beyond its respective tube seat whereby the outersurface of the respective tube ends projecting beyond said pressuremember and the outer face of said pressure member form therebetween anangle having an apex defined as a segment of an arc, and a plurality ofcontinuous welds disposed in successive layers, each of said layersextend- References Cited in the file of this patent UNITED STATESPATENTS 993,883 Schickert May 30, 1911 1,935,063 Scott Nov. 14, 19331,991,429 Straty Feb. 19, 1935 8 McKeever Dec. 7, 1937 Stone Nov. 11,1941 Villiger Oct. 19, 1948 Chapman Oct. 25, 1955 Schoessow Apr. 29,1958 FOREIGN PATENTS Great Britain Nov. 7, 1951

1. FUSION WELDED TUBE ATTACHMENTS TO A PRESSURE MEMBER WHICH COMPRISES APLURALITY OF TUBE SEATS FORMED THROUGH THE WALL OF THE PRESSURE MEMBER,FILLETS FORMED IN THE FACE OF THE PRESSURE MEMBER CONTIGUOUS WITH THEPERIPHERY OF THE TUBE SEATS, FRUSTO-CONICALLY SHAPED TUBE ENDS FITTEDINTO SAID TUBE SEATS AND SO POSITIONED THAT THE CONICAL SURFACES ARETANGENT TO THE ARC OF THE FILLETS WHEREBY THE SURFACES OF THE TUBE ENDSPROJECTING BEYOND SAID PRESSURE MEMBER AND THE OUTER FACE OF SAIDPRESSURE MEMBER FROM OBTUSE ANGLED WELD GROOVES WITH THEIR APEXESDEFINING A SEGMENT OF AN ARC, AND FUSION WELDS IN SUCCESSIVE PASSESCOMPLETELY UNITING SAID TUBES AND PRESSURE MEMBER, EACH OF SAID WELDPASSES BEING SINUOUS AND CONTINUOUS AROUND AT LEAST A SUBSTANTIALPERIPHERAL PORTION OF A PLURALITY OF THE WELD GROOVES.